(i) Field of the Invention
The present invention relates to a washing machine and, more particularly, it relates to a washing machine which comprises an outer tub supported in a frame, and a drum rotatably held about a horizontal supporting shaft in the tub and formed with many bores in its peripheral wall and which is capable of sensing foam generated beyond a permissible amount in the tub in washing the laundry.
(ii) Description of the Prior Art
In a conventional drum washing machine, since the rotation of a drum violently agitates washing water including detergent, foam is generated in a tub. When the foam is excessively generated, it impedes the drum from rotating, and the foam remaining in the tub pollutes rinsing water. Japanese Unexamined Patent Application No. 118195/1984 discloses a drum washing machine. The drum washing machine comprises an outer tub supported in a frame, a drum rotatably held about a horizontal supporting shaft in the tub and formed with many bores in its peripheral wall, rotating means for rotating the drum and sensing means for sensing foam generated beyond a permissible amount in the tub in washing the laundry.
The sensing means senses the foaming in washing the laundry and raises an alarm to urge the user to dilute washing water.
A float is used for the sensing means. When the float is raised by the foam, a sensing switch works.
However, in this prior art embodiment, the user must laboriously manage the defoaming whenever foam is excessively generated. In this case, the defoaming requires only diluting washing water, and thus water in the tub increases. As a result, although the rotation of the drum causes the laundry to beat the wall of the drum, the laundry float in the increased washing water, and hence the desired result of the beating is not obtained.
Although the float is used for the sensing means, the float requires considerable foam to rise. Thus, foaming must be in a fairly advanced stage to be sensed.
It is known that a pair of electrodes can be used for the sensing means utilizing the conduction between those electrodes. However, contrary to using the float, the electrodes become conductive even with a small quantity of foam or water, so that the use of them leads to a large error. Additionally, the electrodes are easily soiled, and therefore the accuracy in sensing is reduced as time elapses.